High-speed ground transportation system

ABSTRACT

A high-speed ground transportation system comprising a tube through which a vehicle is adapted for propulsion from a first station to a second station, the tube having an entrance valve adjacent the first station and an exit valve adjacent the second station adapted, when closed, to block off an evacuated section of the tube from valve-to-valve. Each valve comprises a toroidal cylinder and a gate constituted by a piston movable between a closed position blocking the tube, in which the piston extends out of an open end of the cylinder, and an open position clearing the tube, in which the piston is withdrawn into the cylinder. The gate of the entrance valve is actuated by vacuum derived from the tube; the gate of the exit valve is automatically opened and is closed by action of atmospheric air.

United States Patent lnventors Lawrence K. Edwards;

Bruce E. Skov, both of Palo Alto, Calif. Appl. No. 12,233 l Filed Feb,18,1970 Patented Oct. 5, 1971 Assignee Tube Transit Corp.

Palo Alto, Calif.

Continuation-impart of application Ser. No. 710,582, Mar. 5, 1968, nowabandoned.

HlGH-SPEED GROUND TRANSPORTATION SYSTEM 21 Claims, 21 Drawing Figs.

U.S.Cl 104/156,

Int. Cl 1361b 13/10,

Field of Search 104/138,

Primary ExaminerDrayton E. Hoffman Attorneyl(oenig, Senninger, Powersand Leavitt ABSTRACT: A high-speed ground transportation systemcomprising a tube through which a vehicle is adapted for propulsion froma first station to a second station, the tube having an entrance valveadjacent the first station and an exit valve adjacent the second stationadapted, when closed, to block off an evacuated section of the tube fromvalve-to-valve. Each valve comprises a toroidal cylinder and a gateconstituted by a piston movable between a closed position blocking thetube, in which the piston extends out of an open end of the cylinder,and an open position clearing the tube, in which the piston is withdrawninto the cylinder. The gate of the entrance valve is actuated by vacuumderived from the tube; the gate of the exit valve is automaticallyopened and is closed by action of atmospheric air.

PATENTED 0m 51am SHEET 5 OF 6 mmmm PATENTEUUBT 519?! SHEET 8 BF 6 Ill/lfr HIGH-SPEED GROUND TRANSPORTATION SYSTEM CROSS-REFERENCE TO RELATEDAPPLICATION This application is a continuation-in-part of our copendingUS. Pat. application Ser. No. 710,582 filed Mar. 5, 1968, now abandoned,entitled High-Speed Ground Transportation System.

BACKGROUND OF THE INVENTION The invention is in the field of high-speedground transportation systems particularly of the type shown in US. Pat.No. 3,438,337 of Lawrence K. Edwards, issued Apr. 15, 1969, entitledHigh-Speed Ground Transportation System. In that patent is shown asystem comprising a duct or tube through which a vehicle is adapted forpropulsion as a free piston. Valves are provided adjacent the ends ofthe tube, with stations constituted by airlocks open to the atmosphereoutward of the valves. The section of the tube between the valves ispreevacuated. With the vehicle in a first station, on opening therespective valve acting as an entrance valve, atmospheric air pressureon the rear of the vehicle propels it into said section of the tube.After the vehicle has passed the entrance valve, the latter is closed totrap a slug of air between the entrance valve and the rear of thevehicle. This trapped slug of air expands to apply propulsion force tothe rear of the vehicle, with attenuation of the air behind the vehicleto restore vacuum in the tube, and with compression of air ahead of thevehicle. The valve at the other end of said section of the tube, actingas an exit valve, opens when the pressure ahead of the vehicle reaches apredetermined value and the vehicle passes therethrough and stops in thesecond station, the exit valve then closing. A problem attendant uponsuch a system is that of providing suitable entrance and exit valves,and this invention is directed to the solution of this problem.

SUMMARY OF THE INVENTION Among the several objects of this invention maybe noted the provision of a valve construction suitable for use eitheras an entrance valve or exit valve in a system such as above described,or in similar systems; the provision of such a valve construction which,as regards its use as an entrance valve, is operated by vacuum derivedfrom the evacuated tube, no separate power source for valve operationbeing required; the provision of such a valve construction which, asregards its use as an exit valve, opens automatically, no control actionbeing required; the provision of a valve construction such as describedwhich, while not requiring extensive machining of parts and thereforebeing economical to construct, is adapted effectively to maintain vacuumin the tube; and the provision of such a valve construction adapted tobe readily opened in the event of an emergency.

In general, a valve of this invention, located adjacent a station,comprises a toroidal cylinder on the outside of the tube having itstoroidal axis transverse-to the tube. As used herein, toroidal cylinder"refers to a toroidal cavity or void adapted to accommodate a piston,which will be described. Toroid is used in the classical sense, i.e., itneed not be circular in cross section; however, in this context thetoroidal cylinder and the toroidal piston of one embodiment of theinvention are segments of toroids rather than complete ones. Thiscylinder has one end open to the tube on that side of said axis towardthe station. A gate constituted by a piston is rotatable about said axisbetween a closed position extending out of said open end of the cylinderinto the tube and blocking the tube, and an open position within thecylinder clear of the tube. Control means is provided for effectingopening of the gate enabling use of the valve as an entrance valve. Inits use as an exit valve, the gate of the valve is adapted automaticallyto open via pressure of air built up between the front of theapproaching vehicle and the gate. Other objects and features will be inpart apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. lA-IE are diagrammatic viewsshowing the operation of a section of a high-speed ground transportationsystem equipped with valves of this invention at its entrance and exitends;

FIG. 2 is a longitudinal section of a valve of this invention, the gateof the valve being shown in its closed position blocking the tube;

FIG. 3 is a transverse section on line 33 of FIG. 2;

FIG. 4 is a view similar to FIG. 2 showing the valve in its openposition clear of the tube;

FIG. 5 is a transverse section on line 5-5 of FIG. 4;

FIG. 6 is a transverse section on line 6-6 of FIG. 2;

FIG. 7 is a perspective of the gate per se of the valve;

FIG. 8 is a longitudinal section of a modified version of the valve;

FIG. 9 is a transverse section on line 9-- 9 of FIG. 8;

FIG. 10 is a vertical section on line 10-10 of FIG. 9;

FIG. I l is a longitudinal section showing another modification;

FIG. 12 is a transverse section on line I2-I2 of FIG. II;

FIG. 13 is a side elevation of another modification of the valve;

FIG. 14 is an end view of FIG. 13;

FIG. 15 is a diagrammatic sectional view showing the FIG. 13modification;

FIG. 16 is a view similar to FIG. 15 showing the use of the FIG. 13valve as an entrance valve; and

FIG. 17 is a view similar to FIG. 15 showing the use of the FIG. 13valve as an exit valve.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings,there is indicated at I in FIGS. lA-lE a duct or tube, typically asubterranean tube, in which a vehicle 3 is adapted for propulsion as afree piston by differential pressure between the front and rear of thevehicle. The tube 1 is shown as extending from a station S1 to a stationS2 along the route of a transportation system. Entrance of the vehiclefrom station S1 to the tube is via an entrance valve A at the entranceend of the tube. Exit of the vehicle from the tube to station S2 is viaan exit valve B at the exit end of the tube.

Valves A and B, when closed, block off a section Ia of the tube fromvalve-to-valve between stations SI and S2. Provision is made forevacuating this section of the tube down to low pressure (of the orderof l p.s.i., for example) as by means of suitable evacuating pumpequipment. Each station SI and S2 is in communication with the earthsatmosphere and hence at atmospheric pressure. FIG. IA shows both valvesA and 8 closed, and the vehicle 3 in the station S1 about to start atrip from station S1 to station S2. Section In of the tube between thevalves has been evacuated down to low pressure, e.g., of the order of 1psi. The trip is initiated by opening valve A, resulting in atmosphericpressure, acting on the rearward end of the vehicle, propelling it pastvalve A into the tube section la (see FIG. 18). After the rearward endof the vehicle has passed by valve A and a predetermined amount of air(at atmospheric pressure) has been allowed to enter the tube behind thevehicle, valve A is closed (see FIG. IC). This traps a slug of air inthe tube between valve A and the rearward end of the vehicle, andexpansion of this slug of air causes the vehicle to accelerate until itreaches a point where the pressure ahead of the vehicle is approximatelyequal to the pressure behind the vehicle. The vehicle then begins todecelerate, compressing air between the forward end of the vehicle andvalve B, with attenuation of air behind the vehicle. As the vehicleapproaches valve B, pressure in the tube ahead of the vehicle increasesto the point where it causes valve B to open, and the vehicle comes to astop in station S2, valve B closing behind it.

This invention is particularly concerned with a valve construction andoperating system therefor suitable for each of the entrance and exitvalves A and B. It will be understood that valves A and B may beidentical, and simply installed in reversed positions at the station S1and S2 ends of the tube 1. Referring to FIGS. 2-7, showing the valve Aat station S1, there is indicated at a valve housing located at the topof the tube 1. This housing is formed to provide a toroidal cylindergenerally designated 7 on the outside of the tube. This cylinder has aspan of about 100 to 180. It extends lengthwise with respect to thetube, that is, the toroidal axis of the cylinder extends horizontallycrosswise of the tube above the tube. The toroidal cylinder 7 has arelatively long section 7a of relatively large bore and a relativelyshort section 7b of smaller bore. The small-bore section 7b is on theside of the toroidal axis toward the station S1, and opens into the tube1 as indicated at 7c. A shaft 9 is joumaled in the valve housing 5 onthe toroidal axis of cylinder 7. Keyed on this shaft is a gate 11constituted by a differential rotary toroidal piston which is adapted toswing about the axis of shaft 9 between the closed position in which itis illustrated in FIGS. 2 and 3 extending out of the open end of thecylinder 7 into the tube 1 blocking the tube 1 and an open positionwithin the cylinder wholly withdrawn and clear of the tube (see FIGS. 4and 5). The differential rotary piston 11 has a relatively long section11a having a diameter corresponding to that of the bore of cylindersection 7b, and a relatively short section 11b at its upper end having adiameter corresponding to that of the bore of cylinder section 70. Asshown, the piston 1 1 may be of hollow construction to decrease itsweight. A counterweight 13 for the piston is keyed on shaft 9 outsidecylinder 7. The center of gravity of counterweight and pistoncombination is indicated at G, and it will be observed that thisovercenters as the piston swings between its closed and open position.

The lower end face of the toroidal piston 11 (i.e., the lower end of itssmaller-diameter section 11a) is designated 15. The upper end face ofthe toroidal piston 11 (i.e., the upper end of its larger-diametersection 11b) is designated 17. The face of the step between thelarger-diameter section 11b and the smaller-diameter section of thepiston is designated 19. The valve housing has an auxiliary chamber 21which is in communication with the cylinder 7 at the juncture of thecylinder sections 7a and 7b, the arrangement being such that face 19 ofthe piston (which faces in the direction toward the open end 7c of thecylinder) is subject to pressure in chamber 21.

The cross-sectional diameter of section 11a of the piston 11 is somewhatlarger than the internal diameter of the tube 1, and, when the piston isin its closed position of FIGS. 2 and 3, the margin of its lower endface seals against an annular shoulder or seat 23 in an enlarged section25 of the tube. This section 25 is shaped with a curvature such that thepiston must swing through a predetermined finite angle Y, which may beabout 15, for example, before there is communication of air between thetube and the station.

The valve housing 5 is formed with a port 27 for communication fromcylinder section 7a to the atmosphere. This port is located intermediatethe ends of cylinder 7, nearer to its closed end 7d than its open end70, and has a check valve 29 therein which is adapted to open in thedirection for flow from the cylinder section 70 to the atmosphere.Housing 5 is also formed with a vacuum manifold 31 in communication withthe evacuated tube 1 on the vacuum side of the valve A via a check valve33 which is adapted to open in the direction for flow of air from themanifold 31 into the tube. Manifold 31 is adapted for communication withthe port 27 via a pilot valve 35, and for communication with chamber 21via a pilot valve 37. The latter is a two-way valve, adapted in a firstposition to block communication between manifold 31 and chamber 21 whileestablishing communication between the earth's atmosphere and chamber 21via an atmospheric air inlet port 38, and in asecond position to blockport 38 while establishing communication between manifold 31 and chamber21. The valve housing is also formed with a bleed passage 39 forsupplying air at atmospheric pressure from a chamber 41 in communicationwith the earth 's atmosphere to the closed end 7d of cylinder section70.

The pressure in tube 1 acting on the lower end face 15 of the toroidalgate or piston l 1 is designated P1. The pressure in cylinder section 7aacting on the upper end face 17 of the piston 11 is designated P2. Thepressure in chamber 21 acting on the face 19 of the piston 11 isdesignated P3. The pressure in manifold 31 is designated P4. Thepressure in the tube at the end of the station is designated P5.

Valve B at station S2 is identical to valve A, being installed inreversed position in respect to valve A, as will appear from FIGS.lA-lE.

Operation is as follows:

Considering conditions prior to a trip of the vehicle from station S1 tostation $2, the vehicle will be poised at rest in station S1. Valves Aand B are closed (i.e., their pistons or gates 11 are closed). Section1a of the tube 1 between valves A and B will have been evacuated down tolow pressure, e.g., of the order of 1 p.s.i. Pilot valve 35 of theoperating system for each of valves A and B is closed. Pilot valve 37 ofthe operating system for each of valves A and B is set as shown in FIG.2 for admission of air at atmospheric pressure to chamber 21 whileblocking passage 31 from chamber 21. As to each of valves A and B,pressures Pl-PS are then as follows:

The trip in initiated by opening valve A. This is accomplished byopening pilot valve 35 of valve A, dropping P2 to vacuum. With P1 and P2vacuum, the P3 atmospheric pressure acting on the pressure face 19 ofthe piston 11 swings the piston 11 open. As the piston moves past port27, residual air in cylinder section 7a is trapped and compressed, alongwith air entering cylinder section 7a via the bleed 39. Thus, pressureP2 rises and slows the piston. Ultimately, pressure P2 exceedsatmospheric pressure, and air is forced out through the bleed 39 back tothe atmosphere and the piston is brought to a soft cushioned stop at theposition shown in dotted lines in FIG. 4. After the piston stops, air atatmospheric pressure enters cylinder section 7a through the bleed 39 andslowly moves the piston back to a position as shown in solid lines inFIG. 4 wherein the port 27 is partially opened, and the bleed isbalanced by flow of air (via pilot valve 35, which is open) intomanifold 31.

On opening of the piston or gate 11 of valve A, the vehicle 3 ispropelled into section In of the tube 1 via atmospheric pressure actingon the rear of the vehicle. After the vehicle has passed valve A, thepilot valve 35 of valve A is closed. A predetermined amount ofatmospheric air is allowed to enter section In of the tube 1 from thestation S1 behind the vehicle, and then the piston or gate 11 of valve Ais closed. This is accomplished by setting pilot valve 37 in positionfor communication between chamber 21 and manifold 31, and for blockingthe atmospheric air inlet port 38. At this time, pressures P1 and P5 areatmospheric. Pressure P2 is atmospheric since pilot valve 35 has beenclosed, and the bleed 39 has supplied atmospheric air to the portion ofcylinder section 70 below port 27 (i.e., to the left of face 17 in FIG.4). Thus, a force equal to atmospheric pressure times the area ofpressure face 19 of the piston, i.e., the amount by which the area offace 17 exceeds the effective area of face 15, acts to close the piston.As the piston closes, the air in cylinder section 70 expands, meaningthat pressure P2 decreases. Pressure P1 also decreases due to throttlingof air rushing into the tube 1 behind the vehicle. The

chambers in the valve and its passages are dimensioned so that theforces on the piston cause it to slowly and softly seat against theshoulder 23 at the S1 end of section In of the tube. Pressure P2 incylinder section 70 returns to atmospheric pressure while pressure P1continues to decrease, insuring that the piston face seats firmlyagainst the shoulder 23. Pilot valve 37 is then returned to its initialFIG. 2 position for admission of air at atmospheric pressure to chamber21 while blocking manifold 31 from chamber 21.

When the piston or gate 11 of valve A is closed, expansion of the slugof air trapped in the tube 1 between the rear of the vehicle and thisgate supplies an accelerating force on the rear of the vehicle, and thevehicle continues to accelerate until it reaches the point where thepressure ahead of the vehicle is approximately equal to the pressurebehind the vehicle. The vehicle then begins to decelerate, compressingresidual air in the tube 1 ahead of the vehicle (with attenuation of airbehind the vehicle). Thus, as the vehicle approaches valve B, itcompresses air between the forward end of the vehicle and the end face15 of the piston or gate 11 of valve B, meaning that pressure P1 actingon end face 15 of valve B rises. This may be envisioned by referring toFIG. 2 and considering that it shows valve B (instead of valve A) andstation S2 (instead of station S1) and that the vehicle is approachingthe end face 15 of the piston from the left.

As pressure P1 acting on the end face 15 of piston 11 of valve B rises,pressures P2, P3 and P5 are atmospheric. Pressure Pl ultimately risesabove atmospheric pressure, and a force equal to pressure Pl minus 1atmosphere times the area of the end face 15 of piston 11 of valve Bacts to swing the latter open. The piston travels through angle Y beforecommunication is established between the tube section la and the stationS2. Thus, it travels through this angle before pressure P] is reduced toatmospheric pressure. As the piston 11 of valve B travels through thisangle, the center of gravity G of the counterweight and pistoncombination overcenters (i.e., passes over the axis of rotation of thepiston), and the resulting gravity bias on the piston in conjunctionwith its inertia insure that the piston opens fully. Pressure P2 remainsat atmospheric pressure due to venting via the check valve 29 until thepiston passes the port 27 and, when this occurs, air is trapped incylinder section 7a, causing P2 to rise, slowing the motion of thepiston and bringing it to a soft cushioned stop.

With the piston or gate 11 of valve B open, the vehicle passes throughthe valve and proceeds into the station B. As the rearward end of thevehicle passes the valve B, P1 and P5 drop to vacuum. With P2 and P3 atatmospheric pressure, the piston 11 of valve B starts to close. As itcloses, air in cylinder section 7a is expanded and its pressure P2decreases. As P2 decreases to near vacuum, face 19 of piston 11 actsagainst atmospheric pressure P3 in chamber 21 to slow the motion of thepiston, so that the closing motion is soft. Air then bleeds intocylinder section 7a via the bleed port 39 to raise P2 to atmosphericpressure to insure that the piston seats firmly against shoulder 23.

With valve B closed, entry of air into station S2 behind the vehicle islimited to leakage from atmosphere around the piston 11. Hence, as thetrain proceeds into the station, pressure P5 remains low and the effectis to continue to decelerate the vehicle until it stops in station S2(FIG. 115).

in case of an emergency, it may be necessary to flood the tube with airby opening one or the other or both of valves A and B. This can bereadily accomplished by opening the pilot valve 35 of the desired valveor valves. With the pilot valve 37 in the position shown in FIG. 2 sothat pressure P3 in chamber 21 is atmospheric, the piston 11 opensquickly on opening valve 35 (which effects dropping P2 to vacuum).

F lGS. 8-10 illustrate a modification of the above-describedconstruction for valves A and B, which operates on the same basicprinciples, but which utilizes an auxiliary piston for driving the gateinstead of utilizing a single differential piston as the gate. As showntherein, the valve comprises a main toroidal cylinder 47 extendinglengthwise of the tube 1 at the top of the tube, i.e., the toroidal axisof the cylinder extends horizontally transversely of the tube above thetube. The toroidal bore of this cylinder is of uniform diameterthroughout its extent, and opens at 47: into the tube on that side ofthe toroidal axis toward the station. A shaft 49 is journaled on thetoroidal axis of cylinder 47. Keyed on this shaft is a gate 51constituted by a toroidal piston adapted to swing about the axis of theshaft between a closed position extending out of the open end 470 of thecylinder into the tube blockingthe tube and an open position within thecylinder clear of the tube. This gate or piston 51 is of uniformdiameter throughout its extent, corresponding to the bore of cylinder47, and may be of hollow construction as illustrated to reduce itsweight. The lower end face of piston 51 is designated 53 and its upperend face is designated 55. When the piston is in its closed position,its lower end face 53 seals against shoulder 23 around the tube, asabove.

Cylinder 47 has a port 27a (corresponding to port 27) provided with acheck valve 290 (corresponding to check valve 29), and a vacuum manifold31a (corresponding to manifold 31) provided with a check valve 33a(corresponding to check valve 33). Manifold 31a is adapted forcommunication with port 270 via a pilot valve 35a (corresponding topilot valve 35). A bleed 39a (corresponding to bleed 39) is provided forsupplying air at atmospheric pressure from a chamber 41a (correspondingto chamber 41) to the closed end of cylinder 47.

An auxiliary toroidal cylinder 57 is located alongside the tube 1 andmain cylinder 47 in coaxial relation to the latter. The shaft 49 extendsfrom the main cylinder over to the auxiliary cylinder and has a toroidalauxiliary piston 59 keyed thereon working in the auxiliary cylinder. Theends of this auxiliary piston are designated 59a and 59b. The auxiliarycylinder has a chamber 61 at one end (corresponding to chamber 21) and apilot valve 37a (corresponding to pilot valve 37). The other end of theauxiliary cylinder is interconnected with the main cylinder as indicatedat 63. The auxiliary piston serves as a counterweight for the mainpiston 51, and the center of gravity of the combination of the twopistons is indicated at G. It will be observed that this overcenters asthe main piston 51 swings between its closed and open positions.

The sum of the area of the upper end face 55 of the main piston 51 andthe area of the lower end face 59a of the auxiliary piston is equal tothe area of the upper face 17 of piston 11; the area of the lower endface 53 of the main piston 51 and the area of the upper end face 5% ofthe auxiliary piston 59 are respectively equal to the area of the lowerend face 15 of piston 11 and area of the upper end face 19 of piston 11.Accordingly, the operation of the valve is basically the same as that ofthe valve A or B described above. Thus, as to the entrance valvefunction of the valve shown in FIGS. 8-10, on opening pilot valve 35a,dropping P2 to vacuum, P3 acting on face 59b of the auxiliary piston 59swings the auxiliary piston counterclockwise as viewed in FIG. 10 toswing the piston or gate 51 open, and valve 35a is then closed. Onsetting pilot valve 37a in position for communication between chamber 61and vacuum manifold 31a, the auxiliary piston is swung in clockwisedirection as viewed in FIG. 10 to swing the piston or gate 51 closed. Asto the exit valve function of the valve shown in FIGS. 8-10, rise in P1on approach of the vehicle swings the piston or gate 51 open.

FIGS. 11 and 12 show another modification of the valve construction ofFIGS. 2-7 wherein the bore of the toroidal cylinder is generally ofuniform diameter throughout its length. The cylinder is here designated72 to distinguish it from cylinder 7. The toroidal piston, designatedlie to distinguish it from piston 11, has a cross-sectional diametersomewhat less than that of the bore in cylinder 7e, and is provided atits upper end with a sealing ring 11d, forming an enlargementcorresponding to 1 lb, and providing a pressure face 19a correspondingto face 19. This sealing ring, accommodated in an annular groove 71 inthe piston, is in sliding sealing engagement with the bore of thecylinder. The effect of the smaller cylinder bore 7b of the constructionshown in FIGS. 27 is provided by a sealing ring 73 mounted in thecylinder below chamber 21, with which the piston is in sliding sealingengagement. Two counterweights 13 are shown in FIG. 12 for the piston.Otherwise the construction corresponds to that shown in FIGS. 2-7, andthe operation is the same.

FIGS. 13-17 illustrate a further modification of the valve similar tothe modification in FIGS. 8-10 but having a special gate construction.As shown, this further modification has a main toroidal cylinder orchamber 77 (similar to 47) which curves upward away from tube 1 andwhich is open at its lower end indicated at 770 to the tube on that sideof the toroidal axis toward the station S. The short section of the tube1 on the station side of the valve is referred to as the airlock AL. Ashaft 79 (like shaft 49) is joumaled on the toroidal axis of the chamber77. The latter is of circular cross section and its toroidal axis istransverse to and slightly above the tube. The upper end of the chamber77 is closed as indicated at 77d, with this closure being of inwardlydirected frustoconical form.

The gate of the modification shown in FIGS. 13-17 is designated in itsentirety by the reference numeral 80. It is constituted by two conicalmembers 81 and 83 mounted with their axes generally at right angles on aframe 85 which ex tends radially outward from shaft 79. These twoconical members are preferably formed as hollow conical shells, 81 beingthe lower and 83 the upper of the two. Member 81, which may be referredto as the cap, has its apex secured to. the frame 85 adjacent the outerend of the latter as indicated at 87 and extends on the bottom side ofthe frame with its conical axis at a 45 angle to the frame. Member 83,which may be referred to as the driver, has its apex secured to theframe 85 adjacent the outer end of the frame as indicated at 89 andextends on the top side of the frame with its conical axis at a 45 angleto the frame. The gate 80 is swingable on the axis of shaft 79 betweenthe closed position shown in solid lines in FIG. and the open positionshown in dotted lines in FIG. 15. In the closed position, frame 85 isgenerally at an angle of 45 below horizontal, and the rim 81a of the cap81 is in sealing engagement with the shoulder 23 around the tube 1. Inthe open position, wherein the gate is swung upward, both conicalmembers 81 and 83 are retracted into the chamber 77 clear of the tube 1,the driver (i.e., the upper conical member) nesting over the conicalupper end closure 77d of chamber 77. The driver 83 is preferablyslightly larger than the lower conical member and has a slightly greatermoment arm about shaft 79 than the cap 81. Its rim 83a fits in chamber77 with a small clearance C therebetween.

An auxiliary cylinder or chamber 89 is located alongside the tube 1 andthe main cylinder or chamber 77 in coaxial relation to the latter. Thisauxiliary chamber 89 is a partial toroid, preferably of rectangularcross section, having a lower end 89a which is open to the atmosphereand an upper end 89b which is closed. The shaft 79 extends from the mainchamber into the auxiliary chamber. An impeller 91 in the form of a vaneextends radially outward from the shaft 79 in chamber 89 and has arelatively tight sliding fit in chamber 89 to serve as a piston therein.It is also so weighted and so located on the shaft 79 as to constitute acounterweight for the gate 80, preferably establishing the center ofmass of the entire gate/impeller assembly (which assembly may bereferred to as the rotor R) adjacent to or on the axis of rotation ofthis assembly (i.e., the axis of shaft 79).

The position of the rotor R is controlled by controlling the pressuresin the main chamber 77 and the auxiliary chamber 89. For this purpose,the auxiliary chamber 89 has a vacuum vent 92 having a pilot valve 93therein extending from a point near its upper end to a vacuum manifold95. It also has a relatively large atmospheric vent 97 having a pilotvalve 99 therein and a relatively small atmospheric vent 101 having apilot valve 103 therein at its upper end. These pilot valves are linkedtogether in suitable manner such that the two atmospheric vents 97 and101 are open when the vacuum vent 92 is closed and vice versa.

The main chamber 77 has an atmospheric outlet 105 at the top with acheck valve 107 therein that allows for flow of air out of chamber 77 tothe atmosphere while checking against flow back into the chamber; arelatively large air inlet 109 having a check valve 111 and a pilotvalve 113; and a relatively small air inlet 115 with a pilot valve 117therein. A passage 119 interconnects the tube 1 on the side of gate awayfrom the station and chamber 77 adjacent its upper end. This passage hasa pilot valve 121 therein. Air inlet 109 is connected to passage 119. At123 is indicated a bias port which extends from about the midpoint ofthe outer side of chamber 77 to the vacuum manifold and which has apilot valve 125 and baffles 127 therein.

The relative angular location and size of the vacuum vent 119 andatmospheric outlet of the main chamber 77 and the vacuum vent 92 andatmospheric vents 97 and 101 of the auxiliary chamber shown in thedrawings are illustrative only. The operation of the FIG. 13 valvedepends on the proper location and sizing of each of these items (oneexample of which is shown in FIG. 15). They can be installed atdifferent lateral locations so that any angular location is possible forany of these items.

The operation of the valve shown in FIGS. 13-15 is described below inconjunction with a trip of a train from station S1 to station S2 to FIG.1A. The description uses the nomenclature and valve numbers from FIG.15. For convenience and clarity, FIGS. 16 and 17 show the entrance valveA and exit valve B, respectively, each oriented to correspond to FIG.1A. Further, FIG. 16 shows only those features necessary for the valveto operate as an entrance valve and FIG. 17 shows only the featuresrequired for the valve to operate as an exit valve; the pilot valves orcheck valves associated with the various features not shown are alwaysclosed for the situation illustrated.

ENTRANCE VALVE OPENING (FIG. 16)

Before the trip begins, the train is stationary in station S1, valves Aand B are closed, and the tube has been evacuated (FIG. 1A). Thecondition of the pilot valves of entrance valve A and various pressureswithin this valve are as follows:

A atmospheric, V near vacuum "Between driver and closed end ofmainchamber '"Between impeller and closed end of auxiliary chamber Theforward end of the train is in the airlock so that flow of atmosphericair from the station S1 into the airlock is prevented.

The trip is initiated by opening entrance valve A. This is accomplishedby opening the pilot valve 121 of valve A. The pressure in the mainchamber 77 rapidly decreases as air flows out through the vacuum vent119 into the tube 1. As the pressure nears tube pressure, the rotor Rbegins to move because the torque caused by the pressure differenceacross the driver 83 exceeds that caused by the pressure differenceacross the cap 81. This happens somewhatbefore the pressure reaches tubepressure, since the driver 83 has a slightly larger area and moment armthan the cap 81. As the main chamber 77 drops to tube pressure, therotor R rapidly accelerates until the valve has opened sufficiently forthe atmospheric air in the airlock AL to escape into the tube 1. Theacceleration is somewhat impeded by expansion of the air in theauxiliary chamber 89 until the impeller 91 passes the large atmosphericvent 97, after which there is essentially no pressure difference on theimpeller. After the air has escaped from the airlock AL, the rotor Rcoasts with virtually no acceleration or deceleration until the driver83 begins to cross the vacuum 119 of the main chamber 77. As the drivercrosses the vent, the flow of air out of the chamber 77 is progressivelycut off and the thin air is compressed, causing a braking torque whichbrings the rotor R to a soft stop shortly after the driver has fullypassed the vent 119. The clearance C around the driver 83 providessufficient damping to eliminate any tendency to bounce. It seemsdesirable to locate the center of mass of the rotor R such that theforce of gravity will provide a small torque that insures that the rotorcontinues to move slowly until the driver rests against the conicalclosure 77d of the main chamber 77.

With entrance valve A open, the train proceeds into the tube 1, asindicated in FIG. 1B, and pilot valve 121 of entrance valve A is closed.

ENTRANCE VALVE CLOSING (FIG. 16)

When the rear end of the train has passed entrance valve A, thecondition of the pilot valves of entrance valve A and various pressureswithin the valve are as follows:

The gate assembly 80 is clear of the tube 1 with the driver 83 restingagainst the conical closure 77d of the main chamber Entrance valve A isreadied for closing by opening pilot valve 113, thus opening the largeinlet 109. The valve does not move, however, because no pressuredifferential exists. When the train has proceeded a predetermineddistance into the tube, entrance valve A is closed on command. This isaccomplished by a single operation that closes pilot valves 99 and 103and opens pilot valve 93. The air in the auxiliary chamber 89 is quicklyexhausted via the vacuum vent 92 and atmospheric pressure acting on theimpeller 91 drives the valve A closed. Pressure in the main chamber 77remains essentially equal to tube pressure because of the large inlet109. As the impeller 91 crosses the vacuum vent 92, it begins tocompress the thin air in the auxiliary chamber 89. When the pressureexceeds atmospheric, it slows the rotor R and brings it to soft stopjust before the cap 81 engages the seat 23. Damping is provided by afixed leakage past the impeller 91. This occurs even though a pressuredrop develops across the cap 81 as it impinges upon the flow. Thispressure drop causes the cap 81 to seat firmly as the compressed air inthe auxiliary chamber 89 leaks past the impeller 91. Once entrance valveA is closed,

all valves to be alike so that the trains can be operated in reverse ifnecessary.

EXIT VALVE OPENING (FIG. 17)

As the train approaches station B, the condition of the pilot valves ofexit valve B and various pressures within the valve are as follows:'

With pilot valve 125 open, there is a continuous flow of air 20 from theairlock AL, past the driver 83 which has a small pilot valves 93 and 113are closed and pilot valves 99 and 103 5 amount of clearance C aroundit, into the main chamber 77, and out through the bias port 123 to thevacuum manifold 95. The bias port is sized so that this flow results ina predetermined pressure (P) in the main chamber 77 that is somewhat:less than atmospheric. The bias port may contain baffles as indicatedat 127 so that the pressure drop from the main chamber 77 to the vacuummanifold occurs in several steps, 1 thereby avoiding a potential sourceof noise.

As the train approaches exit valve B, it is rapidly compressing the airahead in the tube 1. When the tube pressure reaches a pressure somewhatless than the bias pressure P in the main chamber 77, the exit valvebegins to open. This occurs before the pressure reaches P because thearea and moment arm of the driver 83 are slightly larger than those ofthe cap 81. The rotor R accelerates rapidly as the tube pressurecontinues to rise. The air in the auxiliary chamber 89 expands until thelarge atmospheric vent 99 is passed by the impeller 91, but theresisting force on the impeller is small compared to that pushing thecap 81.

As the gate assembly moves into the main chamber 77, the pressure in themain chamber 77 rapidly rises to atmospheric since the bias port 123does not have sufficient capacity to hold the bias. When the pressurereaches atmospheric, air exhausts through the atmospheric outlet as wellas the bias port 123 thus maintaining approximately atmospheric pressurein the main chamber 77 until the driver 83 crosses the bias port 123 andatmospheric outlet 105. As it crosses the atmospheric outlet 105, flowis progressively cut off and the driver 83 compresses the air bringingthe rotor R to a soft stop. Again, bounce is prevented by the dampingeffect of the clearance C around the driver 83. The rotor R comes torest with the driver 83 against the conical closure 77d of the mainchamber 77 and the train proceeds through the exit valve B as shown inFIG. 10.

EXIT VALVE CLOSING (FIG. 17)

Pilot Valve Condition Chamber Pressure 93 closed Main 77 V 99 and 103open Auxiliary 89 A 113 closed Tube 1 V 117 closed Airlock AL V 121closed As soon as the rear end of the train has passed through the exitvalve, pilot valve 117 is opened and air enters the main.-

chamber 77 through the small inlet 115. With vacuum operating on theother surfaces of the gate assembly 80, the rotor R accelerates until itreaches a speed that is limited by the flow rate through the small inlet115. The rotor R continues at this speed until the exit valve is nearlyclosed. When the impeller 91 crosses the atmospheric vent 99, it beginscompressing the air trapped in the auxiliary chamber 89 which brakes therotor R and brings it to a stop with the cap 81 seated. Leakage past theimpeller 91 and flow of air through the small atmospheric vent 103allows the compressed air to escape so that the cap 81 remains seatedwith no bounce.

The train comes to a stop in station B as shown in FIG. 1B and the pilotvalve 117 of exit valve B is closed so that the valve is ready to bebiased for the approach of the next train.

When the valve is used only as an exit valve, pilot valves 93, 99, 103,113 and 121 are not used, as indicated in FIG. 17.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is:

1. In a high-speed ground transportation system having an evacuated tubeadapted for propulsion of a vehicle therethrough, a station for thevehicle in communication with the earth's atmosphere, and a valve forthe tube adjacent the station, said valve comprising a toroidal cylinderon the outside of the tube having its toroidal axis transverse to thetube, said cylinder having one end open to the tube on that side of saidaxis toward the station, and a gate constituted by a piston rotatableabout said axis between a closed position extending out of said open endof the cylinder into the tube and blocking. the tube and an openposition within the cylinder clear of the tube.

2. In a high-speed ground transportation system as set forth in claim 1,said cylinder having a port in communication with the atmosphere, and acheck valve for said port adapted to open in the direction for flow ofair from the cylinder to the atmosphere.

3. In a high-speed ground transportation system as set forth in claim 2,said port being located intermediate the ends of the cylinder and beingblocked by the piston as it rotates past said port, and said cylinderhaving a bleed at its other end in communication with the atmosphere forbleeding atmospheric air into said other end of the cylinder.

4. In a high-speed ground transportation system as set forth in claim 3,means for drawing a vacuum in the cylinder via said port.

5. In a high-speed ground transportation system as set forth in claim 4,said means for drawing a vacuum in the cylinder comprising aninterconnection between said port and a source of vacuum, and a pilotvalve in said interconnection.

6. In a high-speed ground transportation system as set forth in claim 5,said source of vacuum being said tube.

7. In a high-speed ground transportation system as set forth in claim 5,said interconnection including a check valve therein adapted to open inthe direction for flow of air from the cylinder to said source ofvacuum.

8. ln a high-speed ground transportation system as set forth in claim 5,said piston being a differential piston having an enlarged sectionadjacent its end toward said other end of the cylinder providing apressure face facing toward said open end of the cylinder, and means forselectively applying atmospheric air or vacuum to said pressure face.

9. In a high-speed ground transportation system as set forth in claim 8,said means for selectively applying atmospheric air or vacuum to saidpressure face comprising a chamber in communication with the cylinder,and a pilot valve having a connection to the atmosphere and a connectionto said source of vacuum and adapted in a first position to establishcommunication from the atmosphere to said chamber and in a secondposition to establish communication between said chamber and said sourceof vacuum.

10. In a high-speed ground transportation system as set forth in claim5, said piston being connected to an auxiliary toroidal piston rotatablein an auxiliary toroidal cylinder, said auxiliary cylinder having oneend interconnected with said first-mentioned cylinder, and means forselectively applying atmospheric air or vacuum to the other end of saidauxiliary cylinder.

11. In a high-speed ground transportation system as set forth in claim10, said means for selectively applying atmospheric air or vacuum tosaid auxiliary cylinder comprising a chamber in communication with saidauxiliary cylinder, and a pilot valve having a connection to theatmosphere and a connection to said source of vacuum and adapted in afirst position to establish communication from the atmosphere to saidchamber and in a second position to establish communication between saidchamber and said source of vacuum.

12. In a high-speed ground transportation system as set forth in claim1, said tube having an enlarged section providing an annular seattherearound engageable by the end of the piston in the tube in theclosed position of the piston.

13. In a high-speed ground transportation system as set forth in claim12, overcentering biasing means for the piston acting to bias it inclosing direction when the piston is in closed position and to bias itin opening direction after the piston has swung open a predeterminedamount.

14. in a high-speed ground transportation system as set forth in claim12, said enlarged section of the tube being shaped so that the piston,in swinging open away from said seat, swings through a finite anglebefore communication of air is established between the tube and thestation.

15. In a high-speed ground transportation system as set forth in claim14, means for counterbalancing the piston with the center of gravity ofthe piston and said counterbalancing means located to overcenter as thepiston swings between closed and open positions so that the piston isbiased in closing direction when in its closed position and in openingdirection after it has swung open through said finite angle.

16. In a high-speed ground transportation system as set forth in claim1, said piston being of hollow toroidal form.

17. In a high-speed ground transportation system as set forth in claim1, said piston comprising a first member constituting a driver and asecond member constituting a cap.

18. In a high-speed ground transportation system as set forth in claim17, said driver and said cap each comprising a conical shell andarranged with their apices adjacent one another and their axes generallyat right angles to one another.

19. In a high-speed ground transportation system as set forth in claim17, said piston being connected to an auxiliary piston rotatable in anauxiliary toroidal cylinder, the first-mentioned cylinder being closedat its other end, a passage having a pilot valve therein interconnectingthe tube and the firstmentioned cylinder adjacent its said closed end,an air inlet interconnecting said passage and the closed end of thefirstmentioned cylinder having a check valve and a pilot valve therein,said auxiliary cylinder being open at one end and closed at the otherand having a vacuum vent adjacent its closed end having a pilot valvetherein, and relatively large atmospheric vent adjacent its closed endand small atmospheric vent at its closedend e a ch having a pilot valvethereir 20. ln a high-speed ground transportation system as set forth inclaim 17, said piston being connected to an auxiliary piston rotatablein an auxiliary toroidal cylinder open at one end and closed at theother, said first-mentioned cylinder being closed at its other end andhaving an atmospheric outlet with a check valve therein adjacent itsclosed end, an air inlet with a pilot valve therein at its closed endand a bias port intermediate its ends connected to vacuum and having apilot valve therein, said auxiliary cylinder having a relatively largeatmospheric vent adjacent its closed end and a relatively smallatmospheric vent at its cl sedcfml each having a pilot valve;

therein.

21. In a high-speed ground transportation system as sethaving a checkvalve and a pilot valve therein, said auxiliary cylinder having a vacuumvent adjacent its closed end having a pilot valve therein, andrelatively large atmospheric vent adjacent its closed end and smallatmospheric rent at its closed end each having a pilot valve therein,said first-mentioned cylinder having an atmospheric outlet with a checkvalve therein adjacent its closed end, an air inlet with a pilot valvetherein at its closed end and a bias port intermediate its endsconnected to vacuum and having a pilot valve therein.

1. In a high-speed ground transportation system having an evacuated tubeadapted for propulsion of a vehicle therethrough, a station for thevehicle in communication with the earth''s atmosphere, and a valve forthe tube adjacent the station, said valve comprising a toroidal cylinderon the outside of the tube having its toroidal axis transverse to thetube, said cylinder having one end open to the tube on that side of saidaxis toward the station, and a gate constituted by a piston rotatableabout said axis between a closed position extending out of said open endof the cylinder into the tube and blocking the tube and an open positionwithin the cylinder clear of the tube.
 2. In a high-speed groundtransportation system as set forth in claim 1, said cylinder having aport in communication with the atmosphere, and a check valve for saidport adapted to open in the direction for flow of air from the cylinderto the atmosphere.
 3. In a high-speed ground transportation system asset forth in claim 2, said port being located intermediate the ends ofthe cylinder and being blocked by the piston as it rotates past saidport, and said cylinder having a bleed at its other end in communicationwith the atmosphere for bleeding atmospheric air into said other end ofthe cylinder.
 4. In a high-speed ground transportation system as setforth in claim 3, means for drawing a vacuum in the cylinder via saidport.
 5. In a high-speed ground transportation system as set forth inclaim 4, said means for drawing a vacuum in the cylinder comprising aninterconnection between said port and a source of vacuum, and a pilotvalve in said interconnection.
 6. In a high-speed ground transportationsystem as set forth in claim 5, said source of vacuum being said tube.7. In a high-speed ground transportation system as set forth in claim 5,said interconnection including a check valve therein adapted to open inthe direction for flow of air from the cylinder to said source ofvacuum.
 8. In a high-speed ground transportation system as set forth inclaim 5, said piston being a differential piston having an enlargedsection adjacent its end toward said other end of the cylinder providinga pressure face facing toward said open end of the cylinder, and meansfor selectively applying atmospheric air or vacuum to said pressureface.
 9. In a high-speed ground transportation system as set forth inclaim 8, said means for selectively applying atmospheric air or vacuumto said pressure face comprising a chamber in communication with thecylinder, and a pilot valve having a connection to the atmosphere and aconnection to said source of vacuum and adapted in a first position toestablish communication from the atmosphere to said chamber and in asecond position to establish communication between said chamber and saidsource of vacuum.
 10. In a high-speed ground transportation system asset forth in claim 5, said piston being connected to an auxiliarytoroidal piston rotatable in an auxiliary toroidal cylinder, saidauxiliary cylinder having one end interconnected with saidfirst-mentioned cylinder, and means for selectively applying atmosphericair or vacuum to the other end of said auxiliary cylinder.
 11. In ahigh-speed ground transportation system as set forth in claim 10, saidmeans for selectively applying atmospheric air Or vacuum to saidauxiliary cylinder comprising a chamber in communication with saidauxiliary cylinder, and a pilot valve having a connection to theatmosphere and a connection to said source of vacuum and adapted in afirst position to establish communication from the atmosphere to saidchamber and in a second position to establish communication between saidchamber and said source of vacuum.
 12. In a high-speed groundtransportation system as set forth in claim 1, said tube having anenlarged section providing an annular seat therearound engageable by theend of the piston in the tube in the closed position of the piston. 13.In a high-speed ground transportation system as set forth in claim 12,overcentering biasing means for the piston acting to bias it in closingdirection when the piston is in closed position and to bias it inopening direction after the piston has swung open a predeterminedamount.
 14. In a high-speed ground transportation system as set forth inclaim 12, said enlarged section of the tube being shaped so that thepiston, in swinging open away from said seat, swings through a finiteangle before communication of air is established between the tube andthe station.
 15. In a high-speed ground transportation system as setforth in claim 14, means for counterbalancing the piston with the centerof gravity of the piston and said counterbalancing means located toovercenter as the piston swings between closed and open positions sothat the piston is biased in closing direction when in its closedposition and in opening direction after it has swung open through saidfinite angle.
 16. In a high-speed ground transportation system as setforth in claim 1, said piston being of hollow toroidal form.
 17. In ahigh-speed ground transportation system as set forth in claim 1, saidpiston comprising a first member constituting a driver and a secondmember constituting a cap.
 18. In a high-speed ground transportationsystem as set forth in claim 17, said driver and said cap eachcomprising a conical shell and arranged with their apices adjacent oneanother and their axes generally at right angles to one another.
 19. Ina high-speed ground transportation system as set forth in claim 17, saidpiston being connected to an auxiliary piston rotatable in an auxiliarytoroidal cylinder, the first-mentioned cylinder being closed at itsother end, a passage having a pilot valve therein interconnecting thetube and the first-mentioned cylinder adjacent its said closed end, anair inlet interconnecting said passage and the closed end of thefirst-mentioned cylinder having a check valve and a pilot valve therein,said auxiliary cylinder being open at one end and closed at the otherand having a vacuum vent adjacent its closed end having a pilot valvetherein, and relatively large atmospheric vent adjacent its closed endand small atmospheric vent at its closed end each having a pilot valvetherein.
 20. In a high-speed ground transportation system as set forthin claim 17, said piston being connected to an auxiliary pistonrotatable in an auxiliary toroidal cylinder open at one end and closedat the other, said first-mentioned cylinder being closed at its otherend and having an atmospheric outlet with a check valve therein adjacentits closed end, an air inlet with a pilot valve therein at its closedend and a bias port intermediate its ends connected to vacuum and havinga pilot valve therein, said auxiliary cylinder having a relatively largeatmospheric vent adjacent its closed end and a relatively smallatmospheric vent at its closed end each having a pilot valve therein.21. In a high-speed ground transportation system as set forth in claim17, said piston being connected to an auxiliary piston rotatable in anauxiliary toroidal cylinder open at one end and closed at the other, thefirst-mentioned cylinder being closed at its other end, a passage havinga pilot valve therein interconnecting the tube and the first-mentionedcylinder adjacent its said closed end, an air inlet interconnecting saidpassage and the closed end of the first-mentioned cylinder having acheck valve and a pilot valve therein, said auxiliary cylinder having avacuum vent adjacent its closed end having a pilot valve therein, andrelatively large atmospheric vent adjacent its closed end and smallatmospheric rent at its closed end each having a pilot valve therein,said first-mentioned cylinder having an atmospheric outlet with a checkvalve therein adjacent its closed end, an air inlet with a pilot valvetherein at its closed end and a bias port intermediate its endsconnected to vacuum and having a pilot valve therein.